The present invention relates to goods-handling doors of the type comprising a raisable curtain, and more particularly to raisable doors that fold concertina-like, comprising a flexible curtain having horizontal reinforcing bars disposed at regular intervals, lifting straps fixed to the bottom bar and passing through rings fixed to at least some of the other bars, and drive means including a shaft disposed above the curtain and onto which the straps are wound. The edges of the curtain and/or the ends of the reinforcing bars are capable of moving in slideways formed in or by lateral uprights which support a top horizontal cross member on which the strap-winding shaft is mounted, possibly together with an electric motor and control members for the motor. It is known that flexible and inextensible means generally in the form of a strip may be provided between adjacent pairs of bars in order to limit the extent to which the bars move apart when the curtain is in its closed position, while not preventing adjacent bars moving towards one another while the curtain is being raised.
One of the problems that arises with a curtain of this nature lies in the folding that takes place when the curtain is raised, both during the raising motion itself and when in the folded position.
When all of the reinforcing bars are provided with rings through which the lifting straps pass, it may happen, e.g. under the influence of wind pressure, that the curtain material folds wrongly going between the bars, and this damages the material and prevents the bars being properly stored side by side in the raised position of the curtain.
Proposals have been made to provide strap-guiding rings on every other bar only. Proper folding is achieved more often in this way, but during curtain-raising, the bundle of bars without rings hangs beneath the bottom bar to which the lifting straps are attached. In the event of unintended wrong operation, a vehicle or a person may strike this bundle of bars or may have it dropped onto them, and the consequences of such an accident may be serious.
An object of the present invention is to solve these two problems.